This invention relates to an image forming method for a heat-developable image forming sheet of the type that is rendered photosensitive by preheating prior to exposure, and exposed to form therein a latent image and then heat-developed to obtain a visible image, and the invention also pertains to apparatus therefor.
A heat-developable image forming sheet, which is rendered by photosensitive preheating prior to exposure, is exposed to form therein a latent image and then is heated to obtain an image (which sheet will hereinafter be referred to simply as the image forming sheet), can provide thereon a visible image only by the dry process, and the image forming sheet is non-photosensitive before it is made photosensitive by preheating. Accordingly, when only a specified area of the image forming sheet is rendered photosensitive by preheating, exposing and then heat-developing, an image is formed only in the specified area, but the other areas which are not made photosensitive at first remain non-photosensitive. Consequently, the abovesaid image forming sheet permits additional recording of an image thereon by preheating and exposing a specified section of an unrecorded area and then heat-developing it.
To render such an image forming sheet photosensitive by preheating is referred to as heat activation, and to render a latent image into a visible image by heating is called heat development.
With a conventional image recording method involving the preheating-exposure-heat development process for the image forming sheet, it is difficult to obtain a sharply-outlined, finely-contrasted, clear image. If a sharply-outlined, finely-contrasted, sharp image can be formed on a desired area of the image forming sheet within a short period of time, then it is possible to enhance superiority and usefulness of the image forming sheet by permitting additional image recording and provide convenient and useful recording means.
An object of this invention is to provide an image forming method and apparatus therefor which substantially increase the sensitivity of the image forming sheet to produce a sharply-outlined, finely-contrasted image and which reduce the time for obtaining a visible image.
Another object of this invention is to provide image forming apparatus which permits handling of the image forming sheet in a light room, and hence is simple-structured, and permits recording and development of information on the image forming sheet by the dry process.
Still another object of this invention is to provide image forming apparatus which, in the case of the image forming sheet having a number of image forming areas, enables the sheet having an image recorded in one of its image forming areas to be taken out of the image forming apparatus and then reinserted thereinto for additional recording of an image in an unrecorded image forming area.
As a result of intensive research, made with a view to achieving the abovesaid objects, for improvement in the image forming method for the image forming sheet, the present inventors have found out that exposure of the image forming sheet in a cooled state after preheating the sheet to render it photosensitive substantially enhances its sensitivity to provide a sharply-outlined, finely-contrasted visible image, and have now completed this invention.